Step One: Start Melting

Place the diced unsalted butter into a medium-sized, non-stick saucepan. It’s helpful to choose a pan with a light-colored interior, as this will allow you to easily monitor the butter’s color change, which is crucial for perfect browning. Place the pan over a steady medium heat.

Step Two: Cook and Observe

As the butter melts, continue to cook it, stirring occasionally to ensure even heating. Once fully melted, slowly bring it to a boil while continuing to stir. You’ll begin to notice the milk solids separating from the clear butterfat and settling at the bottom of the pan. Keep cooking the butter, stirring or swirling gently. The key is to continue this process until these milk solids transform into a beautiful golden amber-brown. Don’t be alarmed if the butter crackles, spits, or foams up – this is a normal part of the process. If you find your butter browning too quickly or unevenly, simply reduce the heat slightly to maintain control.

Step Three: Remove from Heat

As the butter approaches its ideal brown butter stage, the crackling and foaming should start to lessen. At this critical moment, you’ll see those delightful golden-brown flecks at the bottom of the pan and begin to smell a wonderfully rich, nutty aroma. Immediately remove the pan from the heat. The residual heat in the pan can quickly turn brown butter into burnt butter, so prompt action is important. Quickly pour the hot brown butter, including the delicious browned milk solids, into a heat-proof bowl.

Step Four: Cool and Prepare

Allow the brown butter to cool slightly in the heat-proof bowl before incorporating it into your cookie bar dough. It doesn’t need to reach room temperature, but it shouldn’t be scorching hot, as this could inadvertently cook your eggs. If you accidentally browned it a little too much and see a few truly burnt (black) bits, don’t despair! You can carefully pour the butter through a fine-mesh sieve to strain out any unwelcome burnt particles, ensuring your cookie bars maintain a pure, nutty flavor without bitterness.

Step Five: Butter and Sugars

Ensure your brown butter has cooled slightly from its initial hot state. It should still be warm enough to be liquid but not so hot that it would scramble eggs. Add both the soft light brown sugar and the caster sugar to the bowl with the cooled brown butter. Mix these ingredients thoroughly until they are well combined and the mixture is smooth and creamy. This step is crucial for dissolving the sugars and incorporating them evenly into the fat.

Step Six: Wet Ingredients

Next, crack in the two large eggs, one at a time, followed by the vanilla extract. Stir these ingredients into the butter and sugar mixture until everything is fully incorporated and the mixture is smooth and glossy. Avoid over-mixing at this stage; just combine until uniform.

Step Seven: Dry Ingredients

Carefully sift the plain flour, fine sea salt, and bicarbonate of soda into the wet ingredients. Gently mix these dry components into the mixture until just combined and a smooth, cohesive cookie dough forms. Be careful not to overmix the dough, as this can lead to a tougher, less tender cookie bar.

Step Eight: Fold in Chocolate

Add the majority of your chopped dark chocolate chunks to the dough. Reserve a handful of chocolate chunks for sprinkling on top later. Gently fold the chocolate into the dough using a spatula until it’s evenly distributed throughout. This ensures every bite of your cookie bar is packed with chocolatey goodness.

Step Nine: Press and Bake

Press the prepared cookie dough evenly into your lined 20 cm (8-inch) square tin. Once the dough is smoothed into the pan, scatter the reserved chocolate chunks over the top surface, gently pressing them down slightly so they embed into the dough. For that extra gourmet touch, sprinkle generously with flaky sea salt. Transfer the tin to your preheated oven and bake for 25-35 minutes, or until the edges are golden brown and the center looks set but still slightly soft and gooey. The exact baking time will depend on your oven and your preference for gooiness. Allow the cookie bars to cool in the tin for at least 20 minutes before attempting to remove or slice them.

Step Ten: Cool and Slice

After the essential cooling time in the tin, carefully remove the entire slab of cookie bars using the baking paper overhang. Transfer it to a wire rack to cool completely, or to a comfortable temperature for slicing. Once cooled enough to handle without falling apart, use a sharp knife to cut the large cookie slab into individual squares or bars of your desired size. Serve them slightly warm for maximum gooeyness, or at room temperature for a firmer, chewier bite.

• 170 g unsalted butter, diced
• 200 g soft light brown sugar
• 80 g caster sugar
• 2 large eggs
• 1 tsp vanilla extract
• 1 tsp fine sea salt
• 300 g plain flour
• ½ tsp bicarbonate of soda
• 200 g good-quality dark chocolate, chopped into chunks
• Flaky sea salt

1. Preheat your oven to 180ºC (160ºC Fan/350°F). Prepare a 20 cm (8-inch) square baking tin by greasing it and lining it with non-stick baking paper, leaving an overhang on two sides for easy removal. Set aside.
2. First, prepare the brown butter: Place the diced unsalted butter into a medium-sized, light-colored non-stick saucepan. Place it over a low-medium heat and stir gently until the butter is completely melted. Increase the heat to medium and allow the butter to come to a gentle boil, stirring frequently. It will begin to bubble, crackle, and spit – this is perfectly normal, but do exercise caution! Continue cooking the butter, stirring to ensure even browning, until the crackling noises subside and the bubbles diminish. At this stage, you’ll observe a foam appearing on the surface, and the butter’s color will gradually transition from golden-yellow to a light brown, then to a rich, deep amber-brown. This process typically takes between 7-10 minutes, depending on your pan size and heat intensity. Watch the pan closely, as butter can go from perfectly brown to burnt in mere seconds.
3. As soon as small brown flecks begin to appear at the bottom of the pan and you detect a beautiful, nutty aroma reminiscent of hazelnuts, immediately remove the pan from the heat. Promptly and carefully pour the brown butter, including all the browned milk solids, into a medium-sized heat-proof bowl. This action is essential to halt the cooking process. Allow the brown butter to cool slightly in the bowl; it doesn’t need to reach room temperature, but it should no longer be scorching hot. You can prepare brown butter up to 2 weeks in advance and store it, covered, in the fridge. Before using it for the cookie bars, ensure it has softened to room temperature.
4. Once the brown butter has cooled to a warm, pourable state, add both the soft light brown sugar and the caster sugar to the bowl. Mix thoroughly until the sugars are well combined with the butter. Next, add the large eggs, one at a time, followed by the vanilla extract. Stir until all these wet ingredients are fully incorporated. Finally, sift in the plain flour, fine sea salt, and bicarbonate of soda. Mix gently until a smooth cookie dough forms, being careful not to overmix.
5. Fold in the majority of your chopped good-quality chocolate chunks until they are evenly distributed throughout the dough. Reserve a small handful of chocolate chunks for sprinkling over the top later.
6. Press the prepared cookie dough firmly and evenly into the lined baking tin. Sprinkle the reserved chocolate chunks over the top surface of the dough, gently pressing them down slightly to embed them. Generously sprinkle the entire surface with flaky sea salt. Transfer the tin to your preheated oven and bake for 25-35 minutes. The bars are ready when the edges are golden brown and the center still appears slightly soft and gooey (the exact baking time depends on how fudgy you prefer your cookie bars). It’s crucial to leave the cookie bars to cool in the tin for at least 20 minutes before handling.
7. After the essential cooling period, use the baking paper overhang to carefully lift the entire slab of cookie bars out of the tin and transfer it to a wire rack. Once fully cooled (or cooled to your desired temperature for cutting), use a sharp knife to slice them into squares or bars. Enjoy!

To Store: The brown butter can be prepared up to 2 weeks in advance and kept covered and chilled in the fridge. The unbaked cookie dough can also be made up to 3 days in advance, covered, and refrigerated. Once baked, these chocolate chip cookie bars are undeniably best enjoyed on the day they are made. However, they will remain fresh and delicious when stored in a sealed airtight container at room temperature for up to 5 days.

To Reheat: For a wonderfully warm and gooey treat, place a cookie bar onto a microwave-safe plate and heat in 10-second intervals until warmed through and the chocolate is melty.

To Freeze: Baked chocolate chip cookie bars are excellent for freezing. Once completely cooled, slice them into individual portions. Wrap each bar tightly in cling film, then place them in an airtight freezer-safe container or bag. They can be frozen for up to 3 months. To enjoy, simply defrost them at room temperature.

Brown Butter Tip: Browning the butter is an additional step that imparts an incredible amount of nutty, complex flavor to these chocolate chip cookie bars, truly elevating them. However, if you’re very short on time, you can certainly use regular softened unsalted butter instead. If, during the browning process, you notice a few black flecks (indicating burnt milk solids) rather than the desirable golden-brown ones, don’t discard your butter! Simply pour it through a fine-mesh sieve to strain out any burnt bits. Skipping this straining step could impart a bitter flavor to your finished cookie bars.

Chocolate Chunks vs. Chips: This recipe calls for good-quality dark chocolate chopped into chunks, as this creates luscious, melted pools of chocolate in the finished bars. While standard chocolate chips will work, they are designed to hold their shape when baked, so you won’t get the same delightful gooeyness. Feel free to use any flavor or combination of chocolates you like – dark, milk, or white chocolate all work well. You could even create triple chocolate chip cookie bars!

Adding Nuts: For an added layer of crunch and a wonderful praline-like flavor, consider swapping 100g of the chocolate for roughly chopped nuts. Excellent choices include chopped almonds, macadamia nuts, pecans, pistachios, or hazelnuts.